Systems and methods for reducing emissions of internal combustion engines using a fuel processor bypass

Abstract

Described here are systems and methods for reducing emissions of IC engines using a fuel processor bypass. In general, the systems described here include an exhaust pipe, a bypass pipe, a valve, a fuel processor, a fuel injector, and a NO x trap. When the valve is in the open position, the entire exhaust passes through the bypass pipe. When the valve is in a closed position, the entire exhaust passes through the exhaust pipe. In some variations, the systems described here also comprise a pre-combustor, a thermal mass, a mixer, and/or a DPF. Methods for regenerating or desulfating a NO x trap are also described. Typically these methods include introducing exhaust into an exhaust pipe, opening a valve located at the inlet of a bypass pipe, injecting fuel upstream of a fuel processor, and introducing a reducing mixture into a NO x trap. The injection of fuel may be pulsed or continuous.

1. A method for reducing emissions using a system having a fuel processor bypass comprising:
 introducing exhaust into an exhaust pipe, the exhaust pipe connected to a bypass pipe, wherein the bypass pipe comprises an inlet, an outlet, and defines a lumen adapted for the passage of gas therethrough, both the inlet and the outlet of the bypass pipe connecting with the exhaust pipe; 
 introducing the exhaust into a NO x  trap located downstream of the bypass pipe outlet, wherein the NO x  trap comprises an inlet, an outlet, a NO x  absorbing material, and defines a lumen for the passage of gas therethrough, whereby NO x  in the exhaust are absorbed by the absorbing material; 
 opening a valve located at the inlet or outlet of the bypass pipe to regenerate the NO x  trap, such that the entire exhaust flows through the bypass pipe and then the NO x  trap, wherein the valve is configured to move between an open and closed position; 
 injecting fuel into the bypass pipe, upstream of a fuel processor located in the bypass pipe between the inlet and outlet, wherein the fuel processor comprises an inlet, an outlet, a catalytic element, defines at least one lumen adapted for the passage of gas therethrough and produces a reducing mixture comprised of CO and H 2 ; and 
 introducing the reducing mixture into the NO x  trap, wherein the NO x  trap is located downstream of the bypass pipe outlet; and 
 closing the valve to cut the flow to the bypass pipe while maintaining the flow to the NO x  trap. 
 
     
     
       2. The method of  claim 1  where the step of closing the valve maintains the temperature of the catalytic element between a temperature ranging from about 300° C. to about 800° C. 
     
     
       3. The method of  claim 1  wherein the catalytic element is preheated to a temperature ranging from about 500° C. to about 800° C. 
     
     
       4. The method of  claim 1  wherein the exhaust into the NO x  trap contains excess oxygen when NO x  is being adsorbed by the NO x  trap, and the exhaust into the NO x  trap contains essentially no oxygen when the NO x  trap is being regenerated. 
     
     
       5. A system for reducing the concentration of NO x  in an exhaust stream comprising:
 an exhaust system configured to channel an exhaust flow from an engine through an exhaust pipe to a NO x  trap; 
 a bypass pipe configured within the exhaust system, the bypass pipe comprising an inlet, an outlet, and defining a lumen adapted for the passage of gas therethrough, both the inlet and the outlet connecting to the exhaust pipe upstream from the NO x  trap; 
 a valve located at the inlet or outlet of the bypass pipe, wherein the valve is configured to move between a first and second position, such that when the valve is in the first position, the entire exhaust flow passes through the bypass pipe, and when the valve is in the second position, the entire exhaust flow is excluded from the bypass pipe; 
 a fuel processor positioned in the bypass pipe, comprising an inlet, an outlet, a catalytic element and defining at least one lumen adapted for the passage of gas therethrough; and 
 a fuel injector, wherein the fuel injector is located upstream of the fuel processor and is configured to inject fuel into the bypass pipe upstream of the fuel processor; 
 wherein the system operates to place the valve in the first position for regenerating the NO x  trap and in the second position when the NO x  trap is not being regenerated; 
 whereby the entire exhaust flow passes through the NO x  trap regardless of whether the valve is in the first or second position. 
 
     
     
       6. The system of  claim 5  further comprising a thermal mass located downstream of the fuel processor and upstream of the NO x  trap. 
     
     
       7. The system of  claim 5  further comprising a particulate filter, wherein the particulate filter is located downstream of the bypass pipe outlet. 
     
     
       8. The system of  claim 5  wherein the fuel processor further comprises a sulfur trapping material. 
     
     
       9. The system of  claim 5 ,
 wherein the catalytic element of the fuel processor comprises two catalysts in series; 
 the first catalyst is primarily an oxidation catalyst comprising Ni, Rh, Pd, or Pt; and 
 the second catalyst is primarily a reforming catalyst comprising Rh. 
 
     
     
       10. The system of  claim 5  wherein the catalytic element is made of a material selected from the group consisting of ceramic, metal, or mixtures thereof. 
     
     
       11. The system of  claim 5  wherein the fuel processor further comprises an insulating mat. 
     
     
       12. The system of  claim 5  wherein the fuel processor further comprises a radiation barrier. 
     
     
       13. The system of  claim 5  wherein the catalytic element is monolithic. 
     
     
       14. The system of  claim 13  wherein the catalytic element has a wall thickness in the range of 10 to 130 microns. 
     
     
       15. The system of  claim 5  further comprising a pre-combustor located upstream of the fuel processor and downstream of the fuel injector, wherein the pre-combustor comprises a support material having at least two adjacently disposed longitudinal channels for the passage of gas therethrough, wherein the longitudinal channels have inner surfaces and at least a portion of the inner surfaces of at least one of the channels is coated or impregnated with a catalytic material. 
     
     
       16. The system of  claim 15  wherein the pre-combustor is about 0.1 to about 0.7 times the volume of the fuel processor. 
     
     
       17. The system of  claim 15  wherein the support material is made at least in part from an iron-based metal alloy. 
     
     
       18. The system of  claim 15  wherein the support material is made at least in part from an alloy containing aluminum. 
     
     
       19. The system of  claim 15  wherein the support material further comprises a washcoat of zirconium oxide, titanium oxide, hafnium oxide, aluminum oxide, silicon oxide, lanthanum oxide, cerium oxide, magnesium oxide, calcium oxide, strontium oxide barium oxide, chromium oxide, molybdenum oxide, tungsten oxide, or mixtures thereof. 
     
     
       20. The system of  claim 15  wherein the hydraulic diameter of the support material channels is about 0.2 mm to about 10 mm. 
     
     
       21. The system of  claim 15  wherein the catalytic material of the pre-combustor comprises palladium, platinum, or mixtures thereof. 
     
     
       22. The system of  claim 5  comprising at least two fuel processors. 
     
     
       23. The system of  claim 22  wherein the at least two fuel processors are of different size. 
     
     
       24. The system of  claim 22  comprising at least two bypass pipes, wherein the at least two fuel processors are separately positioned in the bypass pipes. 
     
     
       25. The system of  claim 22  wherein at least one fuel processor is in the exhaust pipe, and at least one fuel processor is in the bypass pipe. 
     
     
       26. The system of  claim 25  wherein the at least one fuel processor in the exhaust pipe and the at least one fuel processor in the bypass pipe are of different size.